My 17 year old daughter has what look like stretch marks appear all over her thighs about a month ago and then last week they appeared on the lower part of her legs. She has not gained weight to cause them so we saw doctor. Blood tests showed inflammation of blood vessels. She had several more tests, not sure what they checked, and she came up positive for mononucleosis. Her doctor says the mono caused the vasculitus, but I am concerned there may be some other problem. Can mono cause vasculitis? He did not recommend any treatment, is there a medication she should be taking? Also, we are going on vacation in a week, is there any issue with flying?